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55 Cards in this Set

  • Front
  • Back
What are the two categories of intracellular parasite?
facultative and obligate
Give an example of a facultative intracellular parasite
Salmonella species
Give an example of an obligate intracellular parasite
Chlamydia species
Salmonella is extracellular (T/F)
F. It is intracellular.
Describe Salmonella morphology
facultatively anaerobic
What are Salmonella's three major antigens?
H (flagellar) antigen
O (somatic) antigen
K (capsular) antigen
What shape are bacilli? Cocci?
rod-shaped. spherical.
How is salmonella transmitted?
via feces of infected people or animals via contaminated food or drink
What are the two main diseases associated with Salmonella?
salmonellosis and typhoid fever
Vi is possessed primarily by the Salmonella serovars that cause ___
typhoid fever
What is the naming system for Salmonella?
Salmonella (genus) + species (enterica or bongori) + serovar_type
What are the two species of Salmonella?
enterica, bongori
Where does Salmonella diversity stem from?
an ability to create variation in the H, K, and O antigens
What do serological identification methods use?
They employ antibodies
What are the three serological identification methods?
agglutination tests, ELISAs and Western blots
Define serovars
strains differentiated by serological means
Define biovars
strains differentiated by biochemical or other non-serological means
What are the five Salmonella virulence factors?
-two type III secretion systems
-ability to invade and replicate in host cell
Define pathogenicity island
large region of DNA encoding clusters of genes associated with virulence
SPI_ contains a group of genes called ___ genes responsible for membrane ruffling assoc with invasion of host cell by Salmonella
SPI1, inv
What are the three main serovars of Salmonella enterica?
What are the two most common serovars for infection in the US?
Salmonella are very ___ sensitive
Which Salmonella is one of the causative agents of typhoid fever?
Salmonella enterica serovar Typhi
What is the host range of S. typhi?
humans only
What is the incubation period of typhoid fever?
week to a month after ingestion
Where does S. typhi multiply once eaten?
spleen and liver
Does S. typhi get released into bloodstream?
In what organ does S. typhi persist in chronic carriers?
in the gall bladder
What Salmonella produces a typhoid-like fever in mice, and a self-limiting gastroenteritis in humans?
S. typhimurium
When can S. typhimurium be dangerous to humans?
immunocompromised individuals. bacteria may enter bloodstream
What is the difference between food infection and food poisoning?
food infection = bacteria in food that multiply in gut causing delay in symptom onset

food poisoning = toxins in food (not necessarily any live bacteria)
How does S. typhimurium enter the host in the mouse model?
through 'M' cells = specialized intestinal tract cells that sample antigens from the lumen of the intestine

they translocate and are eaten by macrophages associated with Peyer's patches
S. typhimurium produces harmful enterotoxins (T/F)
What is the function of the S. typhimurium type III secretion system?
to inject proteins into the intestinal cell
What do the injected proteins of S. typhimurium do?
promote internalization of the bacteria
How does the infected host cell respond to the injected proteins of S. typhimurium?
produces inflammatory agents attracting neutrophils

the neutrophils will then produce prostaglandin
What is the role of the host neutrophils during S. typhimurium infection?
produce prostaglandin after migrating to site of infection
What is the effect of prostaglandin on intestinal epithelial cells?
increases the internal concentration of cAMP
What do increased levels of cAMP cause?
inhibition in Na+ uptake, and increase in Cl- secretion
What are Type III secretion systems?
multi-protein assemblies essential to virulence of Gram(-) bacteria, which inject virulence factors into eukaryotic host cells
Type III secretion systems are assocaited with Gram(+) bacteria (T/F)
F. Gram(-) bacteria.
How is the serotype identified during diagnosis?
antigenic analysis of O (cell wall antigen) and H (flagellar antigen) using polyvalent specific antisera
Salmonella entering bloodstream is common (T/F)
type I fimbriae and plasmid-encoded fimbriae are examples of ___
adhesins used by Salmonella
During invasion by Salmonella, what triggers the "ruffling"?
actin rearrangements, mediated by the Salmonella SPI1 system
What pathogenicity island is the Type III injector system on?
What is the function of the proteins that Salmonella injects into endosomes?
alters the structure so that they can no longer fuse with lysosomes
How does Salmonella escape destruction inside the host cell?
It modifies an endosome to prevent lysosome fusion then divides inside of it
Salmonella mutants lacking the SPI2 island are still virulent (T/F)
S. ___ and S. ___ are usually resolved within a week and do not require treatment
typhimurium, enteritidis
Which antibiotics are the treatment of choice for S. typhi infections?
For which serovars of Salmonella has a vaccine been made?
S. typhi only
2 are injected dead bacteria
1 is oral live attenuated
What are the two types of cell-mediated response?
T-cell effector mechanisms

activation of macrophages
SPI_ is responsible for mediating actin rearrangements "ruffling" at cell surface during invasion of host cell, whereas the ___ system of SPI_ is to prevent lysosome fusing with endosome
Type III injector system, SPI2